The impact of agricultural water salvation investment on economics development: Evidence from Eastern China

Agricultural water salvation is the lifeblood of the national economy and is of great significance to the high-quality development of the region. In order to maximize the economic assistances of agricultural water salvation investment, this article focuses on panel data from 2005 to 2019 in 14 provinces in Eastern China, this research constructs an economic development evaluation index system from five dimensions: innovative development, coordinated development, green development, open development and shared development, and uses dynamic panel model to explore the influence relationship and path of Eastern Agricultural water salvation investment on economic development. The results represent that: there is a significant non-linear effect between agricultural water salvation investment and economic growth, showing an inverted U-shaped relationship. Which means that with the expansion of agricultural water salvation investment; economic growth has risen first and then declined. At present, the impact of agricultural water salvation investment in the Eastern region on economic development is in the promotion stage of positive and sustained growth. The recommendation of this research will help the state control in the amount of agricultural water salvation investment in the Eastern region, improve the efficiency of agricultural water salvation investment, and provide support in decision making.


Introduction
Investment in agricultural water salvation construction, as a controlling element that promotes national economic growth, protects people's lives and the ecological environment, occupies a very important position in the relatively backward economically Eastern regions. After the 20 th National Congress of the Communist Party of China, the central government's investment in agricultural water salvation infrastructure has reached a new level. In the late 1980s, in response to an overheated economy and unprecedented inflation rates, China's leaders were forced to adopt a set of stringent constructional macroeconomic policies (Naughton 1995) [1]. As a consequence, after China experienced two years of high inflation, economic growth slowed sharply from 1989 to 1990. The annual growth rate of GDP from 1989 to 1990 was about 4% only, the lowest rate over the entire reform period. After the brief slowdown period, the government responded promptly and implemented a series of policy measures to increase both domestic private and public investments as well as foreign direct investment (FDI). Policies to reticulate the economy included providing a better market environment for private sector development, fiscal and financial expansion, the devaluation of the exchange rate, trade liberalization and the expansion of special economic zones and higher agricultural prices (World Bank 1997) [2]. In accordance with the requirements and instructions of the Party Central Committee, the Eastern region has seized the opportunity and the scale of investment in agricultural water salvation infrastructure has increased significantly. On the one hand, it is to promote the economy development and improve people's livelihood, similarly, it is also to solve the prominent contradiction between economic and social development and agricultural water supply and demand, and to achieve sustainable development of agricultural water resources and economic society [3]. Therefore, studying the impact of agricultural water salvation investment on economic growth is of great significance for optimizing the structure of agricultural water salvation investment and maximizing the economic benefits of agricultural water salvation investment in the eastern region.

Brief literature review
While successful technology transition helps China to increase its agricultural productivity, China may face a great challenge in coming years to grips with water scarcity. Water shortages and increasing competition from industry and domestic use do not provide much hope for large gains in the areas under irrigation and the total output from irrigation expansion   [4,5]. Several domestic scholars have launched many discussions on the relationship between agricultural water salvation investment and economic growth. Xu Bo and Li Wei [6] measured the contribution of agricultural water salvation investment to economic growth and found that agricultural water salvation construction investment has the most direct impact on the primary industry. Koutinas and Peeve (2005) [7] used the general Solow production functions to estimate that agricultural water salvation construction investment has a 10% stimulating effect on GDP growth. Chen Yuanyuan, [8] investigate the relationship between economic development and agricultural water salvation construction investment in the Eastern region from 2002 to 2016, and found that economic development has a significant long-term positive impact on investment in Agricultural water salvation construction. Huang and Rozelle (1995) [9] established a dynamic multiplier analysis model and concluded that the contribution rate of Guangdong's Agricultural water salvation investment to GDP from 2000 to 2017 was 0.65%-2.40%. Chen Ling and Wang Qing [10] found that the completed investment in agricultural water salvation construction has a long-term co-integration relationship with the total output value of agriculture, forestry, animal husbandry and fishery. Existing literature mainly focuses on the discussion of the direction of the influence of agricultural water salvation investment on economic growth and the influence coefficient. Fazakas, L. (2020) [11] examined those processes that directed to the construction of a modern water and sewerage network in Kolozsvár. In his research, he examined the economic features of the project, more precisely whether the city's economic operators supported the establishment of a reliable water supply and sewerage system or they actively opposed it. Furthermore, he outlined the consequences of the 1893 cholera epidemic, which, although it was the last and least virulent epidemic in Kolozsvár, had a major impact on the construction of the sanitation system. Molle and Closas (2020) [12] examined in details the limited effectiveness of national groundwater policies that has been witnessed, emphasizing its political implications. They also analyzed numerous aspects of weak monitoring and enforcement were considered from the viewpoint of the political economy of groundwater economies. Zhao et al. (2020) [13] examined long-term community resilience, which privileges a long-view look at chronic, slow-moving issues affecting communities which attract the attention of researchers and policymakers. To better understand the utility assistance landscape in the Phoenix metropolitan region as a donor to heat resilience among susceptible communities, they formed a joint team of individuals from the university and the Salvation Army and by utilizing exploratory data analysis and advanced spatial analytical methods build a shared understanding of knowledge gaps and verified intuitions. They confirmed that minority groups (African American and Native American) unreasonably require aid.
Nagachevska and Zakharchenko (2014) [14] studied the challenges connected with attracting foreign investments into the agricultural sector of the Ukrainian economy as well as modification of forms of international investments are actual due to the instant needs of realization of innovative development, technological upgrading and strengthening of agricultural sector attractiveness on the world market. They outlined that, Government investment policy in the agricultural sector is observed to combine the resource base and the sources of investment. Furthermore, they provide recommendations how to expand the financing mechanisms for venture projects in the agricultural sector involving angel investors.
Nkamleu, G. B. (2020) [15] examined the theoretical development of watershed management within the context of an exploit research program operating in the highlands of eastern Africa and explored in detail the impressions of "participation" and "integration" in watershed management, and addressed the theoretical and methodological extents of the terms which was discussed in the context of a watershed implementation process, illustrative how "watershed issues" were defined by local users, that how "stakeholders" were defined with respect to those issues, and how contribution and combination may be operationalized in practice.
There are few literatures on dynamic behavior information and panel data that can solve the problem of missing variables. Therefore, based on panel data, this article uses a dynamic model to study the impact of Agricultural water salvation investment on economic development in the Eastern region, and quantifies the contribution of Agricultural water salvation investment to economic and social development. This helps to understand the current situation of Agricultural water salvation investment in the Eastern region and promote the sustainable economic and social development of the Eastern region. China's rapid economic growth and the rise in the nation's overall wealth have been accompanied by widening income inequality. Regional income disparity has been expanding since the 1980s World Bank 2002) [7,16]. Eastern China has grown faster than Central and Western China. The rural reforms increased rural incomes at a faster pace than urban incomes during the early 1980s.
This led to a decline of the urban to rural income ratio from 2.57 in 1978 to 1.86 in 1985. However, after the one-time impact of the rural institutional reforms was exhausted, urban income growth has been consistently higher than that of the rural sector. By 2004, per capita income in the urban areas was 3.21 times that in the rural areas (NSBC 2005) [17]. Rising income disparity within the rural areas has also emerged. For example, the Gini coefficients in rural areas increased from 0.24 in 1980 to 0.31 in 1990 and to 0.37 in 2003 (NSBC-Rural 2004) [18]. While the progress in agricultural and rural development has been notable, there are also many lessons and major challenges ahead. With the transition from a planned to a market-oriented rural economy mostly complete, China's main challenge has shifted to broader development issues. In the coming years, the development process will have to be fundamentally different from the efforts in previous times when meeting the nation's food needs, poverty reduction and economic growth were the main goals. Recently, China surpassed Japan as the world's leading pesticide consumer. Intensive fertilizer and pesticide use can have several adverse effects and concerns about contamination of farm produce and endangering of the agro-ecosystem as well as human health are rising. Environmental stresses have also been occurring such as soil erosion, Stalinization, the loss of cultivated land and decline in land quality (Huang and Rozelle 1995) [9]. [1] show that although China did not record a decline in total cultivated land from the late 1980s to the late 1990s, average potential productivity of cultivated land, or bio-productivity, declined by 2.2% over the same period. In the meantime, a large decline in cultivated land was recorded after the late 1990s due to industrial development and urban expansion.
They were often used in the research of growth, mortality and exploitation of fishery species or even their population structure. Data of length and weight were more important for species whose information of age structure was limited (Sparre & Venema, 1998) [19]. Length frequency data could be used to fit and calculate biological parameters, age structure, population size, mortality (Kohler, 1995) [20] and population evaluation (Salarpouri et al., 2018;Blackwell et al., 2000) [21,22] of aquatic organisms. In the East China Sea, the habitat of many aquatic organisms in the continental shelf waters has been destroyed and the fishery resources have been on constant decline due to excessive fishing intensity and persistent pollution [23].

Analysis of agricultural water salvation investment scale.
Agricultural water salvation construction, as a key support area of national infrastructure construction, is one of the key investment directions of government financial funds [8,10,24,25]. In terms of investment arrangements, the state pays attention to the central and Eastern regions, especially the Eastern regions. The details of the completion of the Eastern Agricultural water salvation investment are shown in Fig 1.

Analysis of sources of agricultural water salvation investment.
With the continuous expansion of Agricultural water salvation investment, the sources of Agricultural water salvation investment have gradually shown diversified characteristics. By categorizing the amount of Agricultural water salvation investment completed in 2005-2019 according to the source of funds, it is found that government investment has always occupied the main position, of which the central government has the largest proportion. Enterprise and private investment, and domestic loans, as new forces, also account for about one-seventh of each year. The use of foreign capital, others, and bonds account for a relatively small proportion, with an annual share of less than 10%.

Analysis of agricultural water salvation investment use.
Based on the data of Agricultural water salvation investment completed in the Eastern region from 2005 to 2019, it is divided into flood control engineering, Agricultural water supply engineering, irrigation engineering, soil and Agricultural water conservation and ecological engineering, Agricultural water logging engineering, hydropower engineering and preliminary work according to purpose. The specific situation is shown in Fig 3.

Economic development in the Eastern region
With the implementation of the Eastern development strategy, new historical achievements have been made in the economic and social development of the Eastern region, which has played an important supporting role in national development [9,26,27]. The Eastern region has entered a period of rapid development, and some provinces have been in the forefront of the country's economic indicators for many years. However, compared with the eastern region, the overall level of economic development in the Eastern region is relatively lagging, with its GDP accounting for only one-fifth of the country's relatively small, although the disposable income of urban residents has been growing, there is still a large gap between the national average and the disposable income, as shown in Fig 4. The Eastern region has entered a period of rapid development, and some provinces have been in the forefront of the country's economic indicators for many years. However, compared with the eastern region, the overall level of economic development in the Eastern region is relatively lagging, with its GDP accounting for only one-fifth of the country's total output, and relatively small investment in fixed assets, and urban residents are at their disposal Although income has been growing, there is still a big gap between it and the national average. Therefore, in the future, the Eastern region should still be the main target of national policy support and investment tilt.

The explained variable
The explained variable is the level of economic development. This article quantifies the economic level of the Eastern provinces from five dimensions: innovative development, coordinated development, green development, development, and shared development, and establishes an indicator system [10,28,29], the results are shown in Table 1. It can be seen from the table that the indicator system consists of 5 first-level indicators, 14 second-level indicators, and 20 third-level indicators. In order to eliminate the differences in dimension, order of magnitude, and orientation among the various indicators, following the suggestion of Bla-gojevi´c et al., 2020 [23,30,31] this paper adopts the entropy method to standardize the selected indicator data. The forward index is processed by formula (1), and the reverse index is processed by formula (2).
Among them, x ij represents the value in the i th row and j th column in the original data, x max represents the maximum value in the j th column in the original data, and x min represents the minimum value in the j th column in the original data. See (3), (4), (5) for specific calculation formulas, and it is stipulated that when q ij = 0, limq ij ; ln q ij = 0 Among them, q ij represents the proportion of u ij in the comprehensive sum of the data; s i represents the index information entropy; w i represents the index weight, the number of columns n = 14, and the number of indicators m = 20. Based on the entropy weight method, the weight of each indicator is calculated, and the comprehensive economic development level of each province is obtained. Based on the entropy weight method, the weight of each indicator is calculated, and the comprehensive economic development level of each province is obtained.

Core explanatory variables
The core explanatory variables are the agricultural water salvation investment and the square item of agricultural water salvation investment in 14 provinces, municipalities and autonomous regions in the Eastern region.

Control variables
In order to better describe the explained variables, this article selects human capital, government intervention, urbanization rate, and degree of opening to the outside world as the control variables of this model. The main variables involved in this article include: economic development (Eco), Agricultural water salvation investment (Agricultural water), Agricultural water salvation investment square item (Agricultural water); intermediary variables include: industrial structure (Ind), technological progress (Rd) and resource allocation (Diskl); control Variables include: human capital (Hum), urbanization level (Urb), government intervention (Gov), and degree of openness (Imp). In order to ensure the stability of the data, the logarithmic value of the agricultural water salvation investment and the degree of openness are taken, and the square term of the agricultural water salvation investment is obtained by taking the logarithmic value of the agricultural water salvation investment and then square [11,22,32].

Model development
Based on the endogenous economic growth model, combined with the economic development indicator system, this paper studies the impact of agricultural water salvation investment on economic development and establishes a basic model, as shown in formula (6).
Among them, Eco it represents the level of economic development of place i in period t, W it is the amount of Agricultural water salvation investment completed in place i in period t, X it is other factors that affect economic development in the same period and the same place, u i is the individual disturbance term, and ε it is random disturbance items. β 0 is the intercept term of the model, β 1 is the variable coefficient of Agricultural water salvation investment, the positive and negative coefficients represent the direction of the influence of agricultural water salvation investment on economic development, and the magnitude indicates the degree of influence. In order to improve the accuracy and scientific model, this article optimizes the above basic model as follows: 4.4.1 Dynamic panel model. In order to assess and clarify whether there is a difference in the impact of agricultural water salvation investment on economic development under different investment scales, this paper introduces the square term of agricultural water salvation investment. Economic development is a process of dynamic changes in the economic structure and profound transformation and upgrading. The impact of the previous level on the current development cannot be ignored. In order to better explore the impact of agricultural water salvation investment on economic development, the third-order lag variable of the explained variable is introduced to construct a dynamic Panel model. The optimized model is shown in (7).
In the formula, Eco it−1 , Eco it−2 , Eco it−3 respectively represent the first, second, and thirdorder lagging terms of the economic development level, and W_q it is the square term of Agricultural water salvation investment, and the meaning of other variables is the same as Eq 6.

Model robustness test.
The robustness of the model has an important impact on the accuracy of the measurement results, and index replacement is a common method to test the robustness of the model Salarpouri et al. 2018 [21], Mukhametzyanov 2020 [33] and Žižović et al. 2020 [34]. The development level of the tertiary industry is one of the important indicators that reflect the level of productivity development of a country or region [31,33,[35][36][37]. This article uses the added value of the tertiary industry as a test index for the replacement economic development level [33,38,39].

Analysis of benchmark results
Considering that the relationship between the explained variable and the core explanatory variable may be mutual: agricultural water salvation investment will promote economic development, and economic development will in turn affect the scale of agricultural water salvation investment, so the model may be endogenous. The results of LR test and Wald test both concluded that there is heteroscedasticity between the model disturbance items. In order to improve the accuracy of the regression results, the system GMM method is used to regress the model after the second-order difference of the variables.
The test results of AR(1) and AR (2) in Table 2 show that the model has first-order autocorrelation, but no second-order autocorrelation, and the disturbance term has no autocorrelation. At the same time, the p-values of Sagan's test are all greater than 0.1, indicating that the selection of instrumental variables is effective. Therefore, it is feasible to use the systematic GMM method to estimate the model. It can be seen from the results that the regression coefficients of the economic development of the three lagging periods are all very significant, indicating that the economic development of the Eastern region will be affected by the previous development level. Further observation of the regression coefficient of agricultural water salvation investment, we found that regardless of the introduction of control variables, the regression coefficient of Agricultural water salvation investment on economic development is positive, and the significance test shows that in the transitional stage of economic growth in Eastern my country, strengthening agricultural water salvation investment to promote Economic development is a viable path choice. For the square term of agricultural water salvation investment, the coefficients are all significantly negative, which shows that with the increase of agricultural water salvation investment, the economy shows a trend of first increase and then decrease, that is, there is an inverted U-shaped relationship between agricultural water salvation investment and economic development and these results are in line with Fazakas, L. (2020) [11]. It shows that the role of agricultural water salvation investment in promoting economic growth is conditionally limited, and a reasonable investment scale is the key to giving full play to the economic benefits of agricultural water salvation investment. Once it exceeds the best advantage, it will hinder economic growth. However, at the present stage, the Eastern region is still far from the best point which confirm the findings of Nagachevska, T. V., & Zakharchenko, V. S. (2014) [14].
The rapid development of the Eastern region still requires government investment and policy support. As far as the control variables are concerned, the regression coefficients of human capital, degree of development, and urbanization are all significantly positive, indicating that higher levels of human capital, degree of openness, and urbanization rate are all conducive to economic development. Although the coefficient of government intervention on economic development is positive, its reliability is not high.

Robustness analysis
Re-regression the value added of the tertiary industry as the explained variable, and the results are shown in Table 2. There is no substantial change in the significance and direction of the regression coefficients, only the value of the coefficient changes. The estimated results still support the conclusion that Agricultural water salvation investment can effectively improve economic development and the relationship between the two is inverted U-shaped, indicating the regression of the model the result is robust.

Concluding remarks and suggestions
Using descriptive data statistics, analyzing from the three aspects of GDP, investment in fixed assets, and people's living standards, it is concluded that the social and economic development of the Eastern region is in a state of continuous growth, but there is a certain gap compared with the eastern region. Some indicators have not reached the national average. Analyzing the current situation and evolution trend of agricultural water salvation investment in the Eastern region from three perspectives of investment scale, investment source and investment purpose, it is found that the total amount of agricultural water salvation investment in the Eastern region has been increasing in the past 14 years. Mainly for irrigation projects, soil and Agricultural water conservation, ecology, and preliminary work have gradually become the focus of investment.
Quantify the economic level of the Eastern provinces from five dimensions, and study the impact of agricultural water salvation investment on economic development. Results demonstrate that there is a significant non-linear effect between Agricultural water salvation investment and economic growth, showing an inverted U-shaped relationship, that is, as the scale of Agricultural water salvation investment expands, economic growth shows a trend of rising first and then falling. It indicates that the expansion of agricultural water salvation investment scale before reaching the optimal scale has a positive impact on economic growth, and more than a certain investment scale will become a factor hindering economic development.
The amount of investment should be controlled to make up for the shortcomings of construction. Give full attention to the government's supporting and guiding role in agricultural water salvation investment to ensure that various types of agricultural water salvation investment can meet the needs of economic development. Optimize the investment structure and implement budget funds. Pay attention to the gradual transformation of agricultural water salvation investment from traditional power generation and irrigation to agricultural water conservation and ecological and agricultural water salvation information construction, timely estimate the investment structure and demand of agricultural water salvation infrastructure in the province, and continuously improve agricultural water salvation guarantee and service capabilities.